It will be interesting to see whether mobile networks do, indeed, allow PlayBook tethering without surcharges, especially as RIM is promoting the device for video conferencing and multimedia playback the OS has full Flash support. If they do, though, the advantage of one SIM and one data plan (for the BlackBerry and the PlayBook) will help businesses to justify deploying the tablet.
Whether consumers will be as taken by the PlayBook remains to be seen. The idea of a "companion" device has been tried before: there are third-party units that already work with BlackBerry phones, and then there was the ill-starred Palm Foleo.
So the PlayBook is probably going to be more of a work book, and although it's tempting to criticise RIM for the slightly silly name, at least it's easier to say than the "it's a business device that works with BES but lets you call the family from the hotel and watch movies on the plane" though that, ultimately, is how most people will use the PlayBook.
